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Depleted oil wells a global warming tool?

In hopes of developing a process that could slow global warming, the Energy Department wants to inject carbon dioxide under depleted Wyoming oil wells.
Reservoirs below these oil wells on the Teapot Dome Naval Petroleum Reserve near Midwest, Wyo., could be used to store carbon dioxide.Robert Hendricks / Casper Star-Tribune via AP file
/ Source: The Associated Press

The government is trying to bury something at its Teapot Dome oil field again. Not secret oil leases, as it did during an infamous scandal of the 1920s, but carbon dioxide — lots of it.

In hopes of developing a process that could slow global warming, the Energy Department wants to inject the greenhouse gas underground into depleted oil reservoirs after converting it into a liquid form.

The Teapot Dome project, now in the planning stages, could be one of the world’s largest test sites for the method. It would store CO2 from a natural gas processing plant more than 300 miles away beneath the 10,000-acre oil field in central Wyoming.

So-called carbon dioxide sequestration has been tested at smaller sites nationwide but never on such a large scale, said Vicki Stamp, a project manager for the Rocky Mountain Oilfield Testing Center, which manages Teapot Dome.

Already used by industry
Used in enhanced oil recovery for decades, pumping carbon dioxide into underground reservoirs is being touted by the Bush administration as one of the most promising ways to counter the greenhouse effect.

“(Carbon dioxide) is the primary global greenhouse gas and it’s growing rapidly,” said Dag Nummedal, director of the University of Wyoming Institute for Energy Research. “During the last four or five years the international consensus is that the most rational, economic and environmentally benign way of getting CO2 out of the atmosphere is to store it underground.

“Right now, the best place to do this is in depleted oil and gas fields.”

Teapot Dome — named for a nearby rock formation — is currently in its preliminary engineering and testing stages. Storage could begin by 2006 and last seven to 10 years, although Nummedal says managers “don’t really know the upper limit yet.”

When a reservoir is full, the pipeline is taken out and the hole sealed up. “The objective is to keep it sealed underground forever, hundreds or thousands of years,” Nummedal said.

The site is projected to store at least 1.6 million tons of carbon dioxide a year when fully operational. It could eventually lead to large-scale testing in other Rocky Mountain states, the Ohio River Valley, Texas Gulf Coast, California and other areas, Nummedal said.

“The long-term plan is to encourage the growth of a new private sector sequestration industry,” he said.

Really long-term storage
Talk of a national CO2 testing center started early last year. But it wasn’t until managers found a source of carbon dioxide later that summer that the idea became a reality.

Anadarko Petroleum Corp., which owns an adjacent oil field, is extending its existing CO2 pipeline from a natural gas processing plant in western Wyoming and has agreed to direct some of its 125 million cubic feet of CO2 to the test site, Nummedal said.

The gas will then be pressurized and injected as a liquid into the reservoirs through a pipeline. It could stay underground for a very long time, since the reservoirs that would store the CO2 held oil and methane gas for millions of years, said Susan Hovorka, a University of Texas researcher.

“That’s not true of other mechanisms,” she said. “If you grow more (trees, which consume carbon dioxide) how do you assure it doesn’t all go up in a forest fire or that another generation decides to go ahead and farm that area?”

Burial can also rid the Earth of a large volume of carbon dioxide in a relatively short amount of time, Hovorka said.

“We’ve got almost all the carbon dioxide emitted in the atmosphere coming from fossil fuels,” she said. “There’s space equivalent in acreage to put all that carbon dioxide back underground.”

If the project pans out, officials hope to capture CO2 from the nation’s power plants, oil and gas refineries and other manufacturing facilities “because that is the CO2 today that is leaking into the atmosphere without any controls on it,” Nummedal said.

One possibility is capturing the gas with scrubbers similar to those attached to smokestacks that remove nitrous oxide and other gases, he said.

Process not cheap
The storage process — particularly compressing the CO2 — is expensive. Some estimates put it as high as $100 per ton, though Nummedal and others said they don’t yet have cost estimates for Teapot Dome.

Even if it is a success, the Teapot Dome project could have little impact by itself.

“Globally we are releasing 7 billion tons of carbon per year,” Nummedal said. “The amount we will be putting away here will be in the hundreds of thousands of tons.”

But he added: “If we look at all the suitable, depleted oil and gas reservoirs in the world, and we were able to fill all of them up, we would be able to store the total global emissions over the next 100 years.”

Some environmentalists worry about gas bubbling through cracks in the Earth or leaking into aquifers that supply drinking water.

“We very clearly need some field demonstrations of a storage system to make sure (we) don’t have any surprises,” said David Hawkins, director of the Natural Resources Defense Council’s Climate Center in Washington, D.C.

Nummedal and others stress they’re testing Teapot Dome reservoirs for those concerns.

“The early steps of this cooperative venture show the classic markings of a win-win proposition for American consumers,” Energy Secretary Spencer Abraham said.